Projeto de um sistema fotovoltaico autônomo de suprimento de energia usando técnica MPPT e controle digital

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

28/08/2009

RESUMO

This work presents the design and development of a battery charger aiming at applications in autonomous photovoltaic systems of low energy consumption, using a Buck type converter with digital control for the loading process based on a digital signal processor TMS320F2812 from Texas Instruments. In order help dimensioning the converter components the photovoltaic set was simulated, its parameters were adjusted according to a commercial module and the results showed similarity with the characteristic curves provided by the manufacturer. Aiming at the maximum energy produced by the photovoltaic panels, thus reducing the charging cycle, a maximum power point tracking MPPT technique was used. In order to choose the most adequate approach, a comparative study was carried on with the three most used MPPT techniques: Constant Voltage - CV, Perturbation and Observation P&O and Incremental Conductance IncCond. The analysis was made based on simulations which have taken into account varied operation conditions of the photovoltaic set. Electrochemical batteries are the ones proposed for the converted photovoltaic energy storage. Through the analysis of the voltage and current curves of such batteries, it is clear that one needs an elaborated control strategy in order to provide an adequate charging cycle. It is desired to completely charge the batteries, within its specified limits, as fast as possible, once the daily generation period is limited. In order to guarantee a complete, fast and secure charge of the batteries, a differentiated control strategy for the Buck converter is presented. When starting the charging process with the batteries discharged, it is desired that the photovoltaic modules operate at their maximum power, so that the batteries will charge as fast as possible. When the battery voltage reaches the maximum specified value (equalizing voltage), the charging process must go on with this constant voltage level and with current limitation in order to avoid damages to the battery due to excessive gas production. A linear model for the Buck converter is obtained, based on state space averaged variables, valid for small signal perturbation around a given operating point. With this model, transfer functions were obtained, which were used for the design of the analogical compensators, which were digitalized through appropriate discrete time approaches. Simulation results obtained using Matlab, as well as experimental tests made in a prototype developed in laboratory, were carried on in order to validate the project and test the charger performance.

ASSUNTO(S)

engenharia elétrica teses.

ACESSO AO ARTIGO

Documentos Relacionados